Mantis Shrimp Navigate Home Using Celestial and Idiothetic Path Integration

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Compound eyes and ocular pigments of crustacean larvae (Stomatopoda and decapoda,brachyura)

Larvae of decapod and stomatopod crustaceans possess paired compound eyes not unlike those of adult crustaceans. However, the visual demands of larval and adult life differ considerably. Furthermore, the eyes of adult stomatopods appear to be far more specialized than those of the larvae. We examined eyes of several stomatopod species just before and after larval metamorphosis. At this time, the entire larval retina is joined by a new, adult‐type retinal array which gradually replaces the remnants of the larval retina. The new retina of the postlarva is anatomically similar to that of the full‐grown adult, and has virtually identical assemblages of intrarhabdomal filters. We determined the photopigments of Gonodactylus aloha, the only species for which we were able to obtain both larval and adult specimens, using microspectrophotometry. The single middle‐wavelength larval rhodopsin (λ_max= 499 nm) disappears at metamorphosis; none of the 10 classes of adult rhodopsins has λ_max between 473 and 510 nm. This metamorphic change of visual pigment does not occur in a comparison species of decapod crustacean, the blue crab Callinectes sapidus. Here, rhodopsins both of the megalops larva and the adult had λ_max at 503–504 nm. The difference between these two species can be explained by the varying ecological requirements of their larvae and adults, and more study of visual pigments in retinas of larval and adult crustaceans is warranted.     

Comparative phylogeography of three codistributed stomatopods: origins and timing of regional lineage diversification in the Coral Triangle

The Indonesian-Australian Archipelago is the center of the world's marine biodiversity. Although many biogeographers have suggested that this region is a "center of origin," criticism of this theory has focused on the absence of processes promoting lineage diversification in the center. In this study we compare patterns of phylogeographic structure and gene flow in three codistributed, ecologically similar Indo-West Pacific stomatopod (mantis shrimp) species. All three taxa show evidence for limited gene flow across the Maluku Sea with deep genetic breaks between populations from Papua and Northern Indonesia, suggesting that limited water transport across the Maluku Sea may limit larval dispersal and gene flow across this region. All three taxa also show moderate to strong genetic structure between populations from Northern and Southern Indonesia, indicating limited gene flow across the Flores and Java Seas. Despite the similarities in phylogeographic structure, results indicate varied ages of the genetic discontinuities, ranging from the middle Pleistocene to the Pliocene. Concordance of genetic structure across multiple taxa combined with temporal discordance suggests that regional genetic structures have arisen from the action of common physical processes operating over extended time periods. The presence in all three species of both intraspecific genetic structure as well as deeply divergent lineages that likely represent cryptic species suggests that these processes may promote lineage diversification within the Indonesian-Australian Archipelago, providing a potential mechanism for the center of origin. Efforts to conserve biodiversity in the Coral Triangle should work to preserve both existing biodiversity as well as the processes creating the biodiversity.     

Long-Wavelength Reflecting Filters Found in the Larval Retinas of One Mantis Shrimp Family (Nannosquillidae)

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The stomatopod rumble: Low frequency sound production in Hemisquilla californiensis

Stomatopods (mantis shrimp), numbering over 450 species, are renowned for their exceptional visual and chemosensory abilities and yet virtually nothing is known about their use of acoustic signals. We present acoustic recordings and analyses of the sounds of a stomatopod, Hemisquilla californiensis. This species generates tonal, low frequency sounds, which we term 'rumble', that are spectrally similar to those produced by African and Asian elephants. The fundamental frequency of the stomatopod rumble ranges from 20 to 60 Hz, with a strong second harmonic. Hemisquilla californiensis appears to generate these sounds through contractions of the posterior mandibular remotor muscle which is coupled to a stiff, lateral extension of the carapace. The sides of the carapace are covered by large, polarized, red spots which vibrate during sound production. Thus, the animals may generate a multi-modal signal by coupling vibrational and visual signals. Hemisquilla californiensis generates the rumble while interacting with potential predators and burrow intruders, suggesting a defensive or territorial function for the sound.     

Shrimps that pay attention: saccadic eye movements in stomatopod crustaceans

Discovering that a shrimp can flick its eyes over to a fish and follow up by tracking it or flicking back to observe something else implies a ‘primate-like’ awareness of the immediate environment that we do not normally associate with crustaceans. For several reasons, stomatopods (mantis shrimp) do not fit the general mould of their subphylum, and here we add saccadic, acquisitional eye movements to their repertoire of unusual visual capabilities. Optically, their apposition compound eyes contain an area of heightened acuity, in some ways similar to the fovea of vertebrate eyes. Using rapid eye movements of up to several hundred degrees per second, objects of interest are placed under the scrutiny of this area. While other arthropod species, including insects and spiders, are known to possess and use acute zones in similar saccadic gaze relocations, stomatopods are the only crustacean known with such abilities. Differences among species exist, generally reflecting both the eye size and lifestyle of the animal, with the larger-eyed more sedentary species producing slower saccades than the smaller-eyed, more active species. Possessing the ability to rapidly look at and assess objects is ecologically important for mantis shrimps, as their lifestyle is, by any standards, fast, furious and deadly.